Photodissociation of HCl and DCl: Polarization of atomic photofragments

Abstract

The complete angular momentum distributions and vector correlation coefficients (orientation and alignment) of ground state Cl(²P_3/2) and excited state Cl(²P_1/2) atoms resulting from the photodissociation of HCl have been computed as a function of photolysis energy. Results for the corresponding H atom partner are also calculated and demonstrate that the H-atom produced is highly spin polarized. The theoretical result s are determined using a time-dependent wave packet treatment of the dissociation dynamics based on ab initio potential energy curves, spin-orbit couplings, and dipole moments that have been reported previously [M. H. Alexander, B. Pouilly and T. Duhoo, J. Chem. Phys. 99, 1752 (1993)]. The theoretical orientation and alignment parameters, a_Q^(K)(p), that describe the coherent and incoherent contributions to the angular momentum distributions from the multiple dissociative states accessed by parallel and perpendicular transitions, are compared to experimental measurements made at 193 nm and excellent agreement is obtained. Theoretical predictions of the a_Q^{( K)}(p) parameters for the isotopically substituted species DCl, for which no experiments have yet been carried out, are reported and contrasted to the analogous HCl results. The results for the H atom spin polarizations are discussed in the context of three static models whose strengths and limitations are highlighted.

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